Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Jan. 11, 2021
Cover [Abstract]
Entity Registrant Name	MGT CAPITAL INVESTMENTS, INC.
Entity Central Index Key	0001001601
Document Type	10-Q
Document Period End Date	Jun. 30, 2020
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity's Current Reporting Status	No
Entity Interactive Data Current	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business Flag	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		506,779,781
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2020